SHAPIRO, M.D.; SCHLUTER, D.; KINGSLEY, D.M.; Howard Hughes Medical Institute and Stanford University School of Medicine; University of British Columbia; Howard Hughes Medical Institute and Stanford University School of Medicine: The genetic control of upper jaw morphology in threespine sticklebacks

Extensive modifications in skeletal feeding structures underlie many of the morphological adaptations of vertebrates to different lifestyles, yet we know very little about the genetic mechanisms that generate vertebrate skeletal diversity. The threespine stickleback fish Gasterosteus aculeatus displays a remarkable range of skeletal morphologies, including modifications of the jaw and dentition in populations adapted to forage in different environments. In this study, we examined the genetic control of the morphology and dentition of the premaxiallae, the paired upper tooth-bearing bones of the jaw, in benthic and limnetic populations of sticklebacks from Priest Lake, British Columbia. Using a recently published genome-wide linkage map of Gasterosteus aculeatus, we identified major quantitative trait loci (QTLs) controlling premaxilla size and number of teeth in offspring from a benthic-limnetic intercross. Furthermore, we identified minor QTLs�some of which are sex-specific�that influence several morphological traits. We are currently extending these studies to fish from additional lakes and trophic regimes. This mapping approach will facilitate molecular studies of the genetic and developmental mechanisms that control evolutionary changes in trophic morphology during adaptive radiations in vertebrates.